<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <!--外部样式-->
    <link rel="stylesheet" href="./start.css">
    <!--内部样式-->
    <style>
        h1{
            color: blue !important;
        }
        h2{
            color: darkred;
        }
    </style>
</head>
<body>
   <!--行内样式-->
   <h1 style="color: red">CSS 样式表</h1>
   <h2>CSS基础</h2>
   <h2>CSS进阶</h2>
   <h3>CSS总结</h3>
</body>
</html>